Practice devices having striking targets are used by athletes in martial arts and martial sports, to hone desirable qualities such as speed, coordination, accuracy and flexibility. For example, one popular practice device is a large punching bag known as a "heavy bag", also known as a "kicking bag" or "body bag", which typically comprises a canvas, vinyl or leather sac filled with a heavy material such as sand, water or the like. The filler imparts resilience and inertial resistance to the bag, reproducing the effect of striking a human opponent and thus allowing an athlete to practice potentially injurious techniques without actually harming an opponent. The heavy bag also provides the advantage of approximating the breadth and height of an opponent, which adds to the realism of the heavy bag as a practice device.
However, the heavy bag provides little feedback to the athlete regarding the accuracy or force of a strike. In general the degree to which the bag deflects under the force of a strike increases with the force of the strike, which provides a rough visual indication of striking power. However, the degree of deflection of the bag is also influenced by other factors such as the point of impact, a strike remote from the anchoring point deflecting the bag more than a higher strike of the same force near the anchoring point, and the angle of impact, since a glancing blow imparts less energy to the bag than a centred strike of equal force and thus deflects the bag less.
At a typical striking speed it is difficult for an athlete, particularly while concentrating on an exercise, to determine whether and to what extent the degree of deflection of the bag may have been attributable to factors other than the force of the strike. The heavy bag thus provides very poor feedback to the athlete, in a sport which relies very heavily on feedback to provide a means and motivation for improving the athlete's skills.
Practice devices are known which provide striking force feedback to an athlete. For example, U.S. Pat. No. 5,605,336 issued Feb. 25, 1997 to Gaoiran et al, which is incorporated herein by reference, provides a shock sensor affixed to a heavy bag for measuring the magnitude of a shock experienced by the bag during a strike. The shock sensor provides a quantified feedback indication to the athlete relating to the force of the strike. However, the shock detected by the sensor is affected by the vertical position at which the strike impacts the bag, and radial point of impact due to the rounded exterior of the bag, and thus still provides only a rough indication of the actual striking force.
U.S. Pat. No. 4,534,557 issued Aug. 13, 1985 to Bigelow et al, which is incorporated herein by reference, provides sensors associated with a variety of different types of striking targets, including a heavy bag and a number of smaller targets, to provide striking force feedback to the user. The smaller targets to some degree avoid the extraneous factors which influence the measured striking force, because limiting the size of the striking surface commensurately reduces the athlete's freedom to strike positions remote from the sensor. However, randomly positioned small targets do not realistically reflect the shape of an opponent's body, nor the arrangement of the sensitive areas of an opponent which martial arts and sports emphasize as striking targets for maximum efficacy.
As such, striking individually positioned small targets for practice does not improve the athlete's ability to selectively strike at susceptible target areas, as opposed to invulnerable or strike-resistant target areas of an actual opponent. The provision of multiple targets with separate sensors also renders this type of equipment complex and expensive.